Spies have more tools at their disposal than bribery, blackmail, and black bag jobs. They've also got pickaxes. When going undercover isn't enough, they go underground to ply their trade. Here are five spy operations that involved digging tunnels to get the job done.

1. OPERATION SILVER

Post-World War II Vienna was divided into four zones, each controlled by either the British, the Americans, the French, or the Soviets. (A central district was jointly managed, with governance rotating monthly between the four countries.) Put four of the world's mightiest powers in one city, and you're going to get some major league espionage.

The Brits ran the best operation. The CIA had only been established in 1947, and was still mismanaged and on the learning curve. (The agency we know today wouldn't be hammered into form until Walter Bedell Smith took charge in 1950.) MI6 had been fishing around Vienna and eventually discovered the communications lines used by the Soviets to talk to Moscow. Out came the hardhats and jackhammers.

MI6 opened a haberdashery as a front, and from the back room of the shop set about digging a seventy-foot tunnel to the Soviet transmission lines. The wiretap was eventually a success, but so too was the clothing store. (MI6 doesn't do anything halfway, as James Bond has repeatedly demonstrated.) The store was so successful, in fact, that foot traffic made effective tradecraft all but impossible. The shop soon boarded up its doors.

2. OPERATION GOLD

The CIA recognized a good thing when they saw it, and wanted in on the wiretapping game. After all, if it worked in Vienna, why not Berlin? While making preparations for the operation, CIA officers uncovered a major defect in their own cryptography equipment. In addition to transmitting coded messages across landlines, American devices transmitted trace echoes of the unencoded messages as well. This problem was quickly solved, but led to a greater discovery: Soviet encryption devices had the same defect, and the Soviets didn't know it. For signals intelligence specialists, this was like tapping a geyser of crude oil.

Operation GOLD was a joint project between U.S. and British intelligence officers. Much like Vienna, Berlin was divided into zones. Allen Dulles, the master of espionage and 5th Director of Central Intelligence, got a tip on the exact location of the Soviet transmission lines in Berlin. To get at those lines, a storage warehouse was constructed as a front for the operation. A 1,500-foot tunnel was excavated twenty feet beneath the soles of Soviet boots. 500,000 calls were recorded.

What the Americans didn't know was that British intelligence had a traitor in their midst. Before the tunnel had even been constructed, George Blake alerted the KGB of the CIA's plans. Notably, however, the KGB never alerted Soviet authorities of the tunnel's existence for fear of revealing Blake's identity. (He was far more valuable in British Intelligence than in prison.) Eventually, however, the Soviets "discovered" the tunnel and expressed public outrage and righteous indignation at such an egregious disregard for international law.

(For whatever reason, this project is still classified. Because who knows what might trigger World War II ½.)

3. OPERATION MONOPOLY

In 1977, the Soviet Union began construction on a new embassy complex in Washington D.C. and the FBI had an idea. Since the days of Hoover, penetrating and bugging foreign embassies was an FBI specialty, and this opportunity simply couldn't be passed up. The plan involved taking advantage of the chaos and cacophony of major construction, and burrowing a tunnel across town and beneath the Soviet embassy. It was, perhaps, the most audacious act of SIGINT-related espionage ever attempted.

Operation MONOPOLY was a joint project between the FBI and National Security Agency. Apartments were purchased to monitor Soviet construction, and another to hide the drill team. Twenty-plus years and hundreds of millions of dollars later, the tunnel project was abandoned. If nothing else, there was the question of which rooms, exactly, they would be able to spy on from beneath the embassy. According to the Spy Museum in Washington, a Special Agent with the FBI summed it up like this: "We had the plans [of the embassy], but you don't know what a room is used for. It might end up being a Xerox room or a storage room. What you want is a coffee room where people talk."

Even had the spy tunnel gone into full operation, it would have been a futile and counterproductive effort. Robert Hanssen, an FBI agent working for the Russians, revealed everything about the tunnel to Russian intelligence. In the end, the only thing MONOPOLY achieved was a massive government expenditure and public humiliation for the U.S. intelligence community.

4. GERMAN TUNNELS FROM THE GREAT WAR

Berlin must have more tunnels under it than that town in Tremors. During the Great War (which would eventually be downgraded to World War I), it is thought that German spies met in subterranean tunnels to exchange information. The tunnels, disused and discovered after the war, had newspapers dated 1918 pasted on the walls.

5. INTER SERVICES RESEARCH BUREAU SPY TUNNELS

In 1940, shelters were constructed beneath the city of London. Tube stations provided access, and tunnels were bored to connect the bombproof shelters. Ultimately, each tunnel facility could accommodate 8,000 people, and were elaborate enough to make even the Vault Dweller from Fallout envious. During the worst of the German assault, even General Eisenhower was once forced to set up shop in one of the shelters.

In 1944, the tunnel shelter at Chancery Lane was allocated for the Inter Services Research Bureau, an arm of MI6. The ISRB initially had intentions of helping the German resistance. Soon, however, it was a hive of 10,000 covert operatives. In 1945, MI6 vanished from the facility, leaving no evidence of its once thriving presence. Questions still remain as to what the massive spy apparatus did beneath the streets of London that year, anyway.